# Programmable Pore Environments in Multivariate ZIF Membranes for Ultra-Selective Helium Recovery from Natural Gas

## TL;DR

Scientists developed a new membrane material that can efficiently and selectively recover helium from natural gas, using less energy than current methods.

## Contribution

A multivariate ZIF membrane strategy is introduced for ultra-selective helium recovery through pore microenvironment programming.

## Key findings

- The membrane achieved a record He/CH4 selectivity of 3174 under industrial feed conditions.
- A two-stage membrane cascade could produce helium with >99.95% purity while reducing energy demand by 83% compared to cryogenic methods.

## Abstract

Helium is an essential yet finite resource with critical
applications
in medical imaging and semiconductor manufacturing, whose production
currently relies almost exclusively on energy-intensive cryogenic
separation of trace helium from natural gas. Membrane-based separations
offer an attractive alternative, but existing materials lack the selectivity
required for industrial deployment. Here, we introduce a strategy
for pore microenvironment programming in multivariate zeolitic imidazolate
framework (MTV-ZIF) membranes, enabling ultraselective helium recovery
under realistic feed gas conditions. By precisely combining Zn2+, 2-methylimidazole, and halogen-substituted benzimidazole
linkers, we create synergistic combinations of steric constraints
and enhanced CH4–framework interactions, which collectively
suppress CH4 transport while preserving rapid He permeation.
Under simulated industrial feed conditions (0.6% He/99.4% CH4 by volume), the best-performing membrane delivered a record He/CH4 selectivity of 3174, with stable operation over 960 h. Process
simulations further show that a two-stage membrane cascade can deliver
>99.95% He purity with an 83% reduction in energy demand compared
to cryogenic distillation. These results highlight multivariate pore
programming in MOFs as a powerful platform for efficient, low-energy
He recovery from natural gas.